The present invention relates to apparatuses for determining a position of a (physical) object and to image processing apparatuses and optical sensor apparatuses possibly used for this. Further, the present invention relates to a method for determining a position of an object. In particular, the present invention relates to determining the position of the object on, at or in relation to a screen or a display area.
Determining the position of a physical object can be applied in the context of user interfaces to enable tracking and/or visualizing of an actual physical position of the physical object, for example by a software running on a computer. There are, for example, so-called tangible user interfaces (TUI). For a subarea of the field of application of tangible user interfaces (TUI), physical objects are to be placed on a computer screen, which is lying flat, whose positions and possibly orientations can be determined automatically by the computer. Thereby, the physical objects can be linked to representations on the screen, such that a movement of these objects can cause an immediate reaction in the computer. The impression that the physical objects belong to the representations on the screen is created, the representations become directly ‘tangible’. The technical teachings disclosed herein describe techniques efficiently allowing such position recognition.
One method of detecting the position of the object is to sense the object by a camera which is either mounted above or below the screen (e.g. in connection with a transparent projection screen), which is, for example applied in the product Microsoft Surface™. In a refinement of this technology, marketed as Microsoft Surface 2, a matrix of light-sensitive sensors replacing the camera is integrated directly into the screen. Thus, in these approaches, either additional external cameras and/or specific screen hardware is necessitated. Another known approach (see, for example, International Patent Application having the publication number WO 01/15059 A2 from 2000) manages without specific screens. In this approach, image signals are shown on the screen, from which the position on the screen can be detected when the same is recognized and evaluated by the applied objects. The applied objects have optical sensors and a radio channel to the computer to be able to recognize the position and to transmit the same to the computer.
Typically, it is desirable that invisibility or at least low perceptibility of the superimposed information patterns can be ensured. In the mentioned International Patent Application WO 01/15059 A2, different options are described how information signals can be superimposed on a background image to thereby detect the position of the physical objects. In one of these variations, the superimposed information is location-dependent with respect to the screen, i.e. different patterns, whose recognition allows a direct conclusion regarding the location, are superimposed in different areas of the screen. These patterns can be formed either in the area or in time. In particular, it is intended that the patterns are active simultaneously for all image areas. This results in the desire that the superimposed patterns are to be invisible to the user. For solving this problem, WO 01/15059 A2 merely suggests the usage of specific screen hardware which can radiate light signals in the non-visible range. A solution with a conventional screen is not described. The present invention describes how it is possible to embed patterns, which lie below the human threshold of perception but are still recognizable by the objects, into normal screens, when patterns, sensor HW and signal processing are selected appropriately. This is the principle of “watermark embedding”.
The published US patent application with the publication number US 2007/0001950 A1 describes a method and a system for presenting a data on a medium for sensing by an input apparatus. The method embeds a symbol design, such as an embedded interaction code (EIC) into an image on a display screen, such as a liquid crystal display (LCD). A grid having a plurality of pixels defines a size of an EIC pattern on an LCD. One area of the grid is used to embed position data and/or metadata information.
It is the object of the present invention to provide an apparatus and a method for determining the position of an object that can cooperate with normal screen hardware or projection hardware, and wherein a pattern used by the apparatus or the method is possibly not or only slightly perceptible by a human viewer.